Sequelize.js -如何访问相关的内存项

Question

我有两个模型，一个叫User，第二个叫Preferences。两者之间存在关联:

User.hasOne(Preferences)

假设user是user的一个实例，而pref是Preferences中的一个和像

这样的语句

user.setPreferences(pref)

然后AFAIU用户和首选项以某种方式链接(即使尚未存储在数据库中)。然后，从用户的角度来看，我如何访问它的相关首选项。使用getPreferences()将调用DB，这在这种情况下是无用的…我已经检查了用户。首选项和用户。

是否有一种简单的方法来处理关联项?

Answer 1

user.Preferences是在代码中显式请求时填充的:

const user2: User = await User.findOne({ where: { id: 1 }, include: [Preference] });
console.log(user2.Preferences); // it's only populated when explicitly requested in code

它将发送SQL到DB。否则为undefined

最简单的方法是在User模型类上创建私有属性，并在成功执行user.setPreferences(pref)后为每个用户实例存储相关的preferences模型实例，而不调用DB。

。使用"sequelize": "^5.21.3"

import { sequelize } from '../../db';
import { Model, DataTypes, HasManyGetAssociationsMixin, HasManySetAssociationsMixin } from 'sequelize';
class User extends Model {
public id!: number;
public getPreferences!: HasManyGetAssociationsMixin<Preference>;
public setPreferences!: HasManySetAssociationsMixin<Preference, Preference['id']>;
public readonly Preferences?: Preference[];
public _inMemoryAssociatedPreferences: Preference[] = [];
}
User.init({}, { sequelize });
class Preference extends Model {
public id!: number;
public name!: string;
}
Preference.init({ name: DataTypes.STRING }, { sequelize });
User.hasMany(Preference);
Preference.belongsTo(User);
(async function test() {
await sequelize.sync({ force: true });
await User.create({ id: 1 });
const user: User = await User.findOne({ where: { id: 1 } });
const pref = await Preference.create({ id: 1, name: 'a' });
await user.setPreferences(pref);
user._inMemoryAssociatedPreferences = [pref];
// elsewhere
console.log('in memory preferences:', user._inMemoryAssociatedPreferences);
await sequelize.close();
})();

输出:

Executing (default): DROP TABLE IF EXISTS "Preference" CASCADE;
Executing (default): DROP TABLE IF EXISTS "User" CASCADE;
Executing (default): DROP TABLE IF EXISTS "User" CASCADE;
Executing (default): CREATE TABLE IF NOT EXISTS "User" ("id"   SERIAL , PRIMARY KEY ("id"));
Executing (default): SELECT i.relname AS name, ix.indisprimary AS primary, ix.indisunique AS unique, ix.indkey AS indkey, array_agg(a.attnum) as column_indexes, array_agg(a.attname) AS column_names, pg_get_indexdef(ix.indexrelid) AS definition FROM pg_class t, pg_class i, pg_index ix, pg_attribute a WHERE t.oid = ix.indrelid AND i.oid = ix.indexrelid AND a.attrelid = t.oid AND t.relkind = 'r' and t.relname = 'User' GROUP BY i.relname, ix.indexrelid, ix.indisprimary, ix.indisunique, ix.indkey ORDER BY i.relname;
Executing (default): DROP TABLE IF EXISTS "Preference" CASCADE;
Executing (default): CREATE TABLE IF NOT EXISTS "Preference" ("id"   SERIAL , "name" VARCHAR(255), "UserId" INTEGER REFERENCES "User" ("id") ON DELETE SET NULL ON UPDATE CASCADE, PRIMARY KEY ("id"));
Executing (default): SELECT i.relname AS name, ix.indisprimary AS primary, ix.indisunique AS unique, ix.indkey AS indkey, array_agg(a.attnum) as column_indexes, array_agg(a.attname) AS column_names, pg_get_indexdef(ix.indexrelid) AS definition FROM pg_class t, pg_class i, pg_index ix, pg_attribute a WHERE t.oid = ix.indrelid AND i.oid = ix.indexrelid AND a.attrelid = t.oid AND t.relkind = 'r' and t.relname = 'Preference' GROUP BY i.relname, ix.indexrelid, ix.indisprimary, ix.indisunique, ix.indkey ORDER BY i.relname;
Executing (default): INSERT INTO "User" ("id") VALUES ($1) RETURNING *;
Executing (default): SELECT "id" FROM "User" AS "User" WHERE "User"."id" = 1;
Executing (default): INSERT INTO "Preference" ("id","name") VALUES ($1,$2) RETURNING *;
Executing (default): SELECT "id", "name", "UserId" FROM "Preference" AS "Preference" WHERE "Preference"."UserId" = 1;
Executing (default): UPDATE "Preference" SET "UserId"=$1 WHERE "id" IN (1)
in memory preferences: [
Preference {
dataValues: { id: 1, name: 'a', UserId: null },
_previousDataValues: { id: 1, name: 'a', UserId: null },
_changed: { id: false, name: false, UserId: false },
_modelOptions: {
timestamps: false,
validate: {},
freezeTableName: true,
underscored: false,
paranoid: false,
rejectOnEmpty: false,
whereCollection: [Object],
schema: null,
schemaDelimiter: '',
defaultScope: {},
scopes: {},
indexes: [],
name: [Object],
omitNull: false,
sequelize: [Sequelize],
hooks: {}
},
_options: {
isNewRecord: true,
_schema: null,
_schemaDelimiter: '',
attributes: undefined,
include: undefined,
raw: undefined,
silent: undefined
},
isNewRecord: false
}
]